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📄 chap04.htm

📁 数字图像处理入门. 一位图像处理高手写的书. 从图像处理的最基础开始,然后慢慢以一些例子做说明,进入图像处理的更高阶段.学习图像处理不可多得的比较朴实的书
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    </span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
    15,47,7,39,13,45,5,37,</p>
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
    </span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
    63,31,55,23,61,29,53,21};</p>
  <p style='line-height:18.0pt'><span lang=EN-US>BOOL LimbPatternM3(HWND hWnd)</span></p>
  <p style='line-height:18.0pt'><span lang=EN-US>{</span></p>
  <p style='line-height:18.0pt'>DWORD&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
    OffBits,BufSize</p>
  <p style='line-height:18.0pt'>LPBITMAPINFOHEADER&nbsp;&nbsp; lpImgData;</p>  
  <p style='line-height:18.0pt'>LPSTR&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; lpPtr;</p>  
  <p style='line-height:18.0pt'>HLOCAL&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; hTempImgData;</p>  
  <p style='line-height:18.0pt'>LPBITMAPINFOHEADER&nbsp;&nbsp; lpTempImgData;</p>  
  <p style='line-height:18.0pt'>LPSTR&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; lpTempPtr;</p>  
  <p style='line-height:18.0pt'>HDC&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; hDc;</p>  
  <p style='line-height:18.0pt'>HFILE&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; hf;</p>  
  <p style='line-height:18.0pt'>LONG&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; x,y;</p>  
  <p style='line-height:18.0pt'>unsigned char&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; num;</p>  
  <p style='line-height:18.0pt'><span
lang=EN-US>OffBits=bf.bfOffBits-sizeof(BITMAPFILEHEADER);</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>BufSize=OffBits+bi.biHeight*LineBytes;//</span><span
style='font-family:宋体;"Times New Roman"'>要开的缓冲区大小</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>if((hTempImgData=LocalAlloc(LHND,BufSize))==NULL)</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>{</span></p>
  <p style='line-height:
18.0pt'><span lang=EN-US>MessageBox(hWnd,&quot;Error alloc memory!&quot;,&quot;Error 
    Message&quot;,MB_OK|</span></p>
  <p style='line-height:
18.0pt'><span lang=EN-US>MB_ICONEXCLAMATION);</span></p>
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp; </span>return FALSE;</p>  
  <p style='line-height:18.0pt'><span
lang=EN-US>}</span></p>
  <p style='line-height:18.0pt'>lpImgData=(LPBITMAPINFOHEADER)GlobalLock(hImgData);&nbsp;&nbsp;&nbsp; 
  </p>
  <p style='line-height:18.0pt'><span
lang=EN-US>lpTempImgData=(LPBITMAPINFOHEADER)LocalLock(hTempImgData);</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>//</span><span style='font-family:宋体;
&quot;Times New Roman&quot;'>拷贝头信息和位图数据</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>memcpy(lpTempImgData,lpImgData,BufSize);</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>for(y=0;y&lt;bi.biHeight;y++){</span></p>
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span>//lpPtr<span
style='font-family:宋体;"Times New Roman"'>为指向原图位图数据的指针</span></p>
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span>lpPtr=(char   
    *)lpImgData+(BufSize-LineBytes-y*LineBytes);</p>
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span>//lpTempPtr<span
style='font-family:宋体;"Times New Roman"'>为指向新图位图数据的指针</span></p>
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span>lpTempPtr=(char   
    *)lpTempImgData+(BufSize-LineBytes-y*LineBytes);</p>
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span>for(x=0;x&lt;bi.biWidth;x++){</p>
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
    </span>num=(unsigned char)*lpPtr++;</p>  
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
    </span>if ( (num&gt;&gt;2) &gt; BayerPattern[y&amp;7][x&amp;7]) //<span  
style='font-family:宋体;"Times New Roman"'>右移两位后做比较</span></p>
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
    </span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; *(lpTempPtr++)=(unsigned char)255;   
    //<span style='font-family:宋体;
&quot;Times New Roman&quot;'>打白点</span></p>
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
    </span>else *(lpTempPtr++)=(unsigned char)0; //<span style='font-family:宋体;  
&quot;Times New Roman&quot;'>打黑点</span></p>
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span>}</p>
  <p style='line-height:18.0pt'><span
lang=EN-US>}</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>if(hBitmap!=NULL)</span></p>
  <p style='line-height:18.0pt'><span>&nbsp;&nbsp;&nbsp; </span>DeleteObject(hBitmap);</p>
  <p style='line-height:18.0pt'>hDc=GetDC(hWnd);&nbsp;&nbsp;&nbsp; </p>
  <p style='line-height:18.0pt'><span
lang=EN-US>//</span><span style='font-family:宋体;
&quot;Times New Roman&quot;'>形成新的位图</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>hBitmap=CreateDIBitmap(hDc,(LPBITMAPINFOHEADER)lpTempImgData,</span></p>
  <p style='line-height:
18.0pt'><span lang=EN-US>(LONG)CBM_INIT,</span></p>
  <p style='line-height:
18.0pt'><span lang=EN-US>(LPSTR)lpTempImgData+</span></p>
  <p style='line-height:
18.0pt'><span lang=EN-US>sizeof(BITMAPINFOHEADER)+</span></p>
  <p style='line-height:
18.0pt'><span lang=EN-US>NumColors*sizeof(RGBQUAD),</span></p>
  <p style='line-height:
18.0pt'><span lang=EN-US>(LPBITMAPINFO)lpTempImgData,</span></p>
  <p style='line-height:
18.0pt'><span lang=EN-US>DIB_RGB_COLORS);</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>hf=_lcreat(&quot;c:\\limbm3.bmp&quot;,0);</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>_lwrite(hf,(LPSTR)&amp;bf,sizeof(BITMAPFILEHEADER)); </span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>_lwrite(hf,(LPSTR)lpTempImgData,BufSize);</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>_lclose(hf);</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>//</span><span style='font-family:宋体;
&quot;Times New Roman&quot;'>释放内存和资源</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>ReleaseDC(hWnd,hDc);</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>LocalUnlock(hTempImgData);</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>LocalFree(hTempImgData);</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>GlobalUnlock(hImgData);</span></p>
  <p style='line-height:18.0pt'><span
lang=EN-US>return TRUE;</span></p>
  <p style='line-height:18.0pt'><span lang=EN-US>}</span><span
lang=EN-US style='font-size:9.0pt;'></span></p>
  <h2> <span
lang=EN-US>4.2</span> <span lang=EN-US> </span><a name="_Toc486331879"></a><a  
name="_Toc486332879"></a><a name="_Toc486338988"></a><a name="_Toc454810853"></a><a
name="_Toc454856627"><span><span>抖动法</span></span></a></h2>
  <p style='line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>让我们考虑更坏的情况：即使使用了图案化技术，仍然得不到要求的灰度级别。举例说明：假设有一幅</span><span
lang=EN-US>600</span><span style='font-family:宋体;
&quot;Times New Roman&quot;'>×</span><span lang=EN-US>450</span><span
style='font-family:宋体;"Times New Roman"'>×</span><span lang=EN-US>8bit</span><span style='font-family:
宋体;&quot;Times New Roman&quot;'>的灰度图，当用分辨率为</span><span
lang=EN-US>300dpi</span><span style='font-family:宋体;
&quot;Times New Roman&quot;'>×</span><span lang=EN-US>300dpi</span><span
style='font-family:宋体;"Times New Roman"'>的激光打印机将其打印到</span><span lang=EN-US>8</span><span
style='font-family:宋体;"Times New Roman"'>×</span><span lang=EN-US>6</span><span style='font-family:
宋体;&quot;Times New Roman&quot;'>英寸的纸上时，每个象素可以用</span><span
lang=EN-US>(2400/600)</span><span style='font-family:宋体;"Times New Roman";"Times New Roman"'>×</span><span
lang=EN-US>(1800/450)=4</span><span style='font-family:宋体;"Times New Roman";"Times New Roman"'>×</span><span
lang=EN-US>4</span><span style='font-family:宋体;
&quot;Times New Roman&quot;'>个点大小的图案来表示，最多能表示</span><span
lang=EN-US>17</span><span style='font-family:宋体;
&quot;Times New Roman&quot;'>级灰度，无法满足</span><span lang=EN-US>256</span><span
style='font-family:宋体;"Times New Roman"'>级灰度的要求。可有两种解决方案：</span><span lang=EN-US>(1)</span><span
style='font-family:宋体;"Times New Roman"'>减小图象尺寸，由</span><span lang=EN-US>600</span><span
style='font-family:宋体;"Times New Roman"'>×</span><span lang=EN-US>450</span><span style='font-family:
宋体;&quot;Times New Roman&quot;'>变为</span><span
lang=EN-US>150</span><span style='font-family:宋体;
&quot;Times New Roman&quot;'>×</span><span lang=EN-US>113</span><span
style='font-family:宋体;"Times New Roman"'>；</span><span lang=EN-US>(2)</span><span style='font-family:
宋体;&quot;Times New Roman&quot;'>降低图象灰度级，由</span><span
lang=EN-US>256</span><span style='font-family:宋体;
&quot;Times New Roman&quot;'>级变成</span><span lang=EN-US>16</span><span
style='font-family:宋体;"Times New Roman"'>级。这两种方案都不理想。这时，我们就可以采用“抖动法”</span><span lang=EN-US>(dithering)</span><span
style='font-family:宋体;"Times New Roman"'>的技术来解决这个问题。其实刚才给出的算法就是一种抖动算法，称为规则抖动</span><span lang=EN-US>(regular   
    dithering)</span><span style='font-family:宋体;
&quot;Times New Roman&quot;'>。规则抖动的优点是算法简单；缺点是图案化有时很明显，这是因为取模运算虽然引入了随机成分，但还是有规律的。另外，点之间进行比较时，只要比标准图案上点的值大就打白点，这种做法并不理想，因为，如果当标准图案点的灰度值本身就很小，而图象中点的灰度只比它大一点儿时，图象中的点更接近黑色，而不是白色。一种更好的方法是将这个误差传播到邻近的象素。</span></p>
  <p style='line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>下面介绍的</span><span lang=EN-US>Floyd-Steinberg</span><span
style='font-family:宋体;"Times New Roman"'>算法就采用了这种方案。</span></p>
  <p style='line-height:18.0pt'><span
style='font-family:宋体;"Times New Roman"'>假设灰度级别的范围从</span><span lang=EN-US>b(black)</span><span
style='font-family:宋体;"Times New Roman"'>到</span><span lang=EN-US>w(white)</span><span
style='font-family:宋体;"Times New Roman"'>，中间值</span><span lang=EN-US>t</span><span style='font-family:
宋体;&quot;Times New Roman&quot;'>为</span><span
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